Orthodontic pliers can comprise two separable parts, each of which has a handle and some type of jaw device. The parts are generally joined by a hinge which must be disassembled to separate the parts. Examples of such separable pliers include those disclosed in U.S. Pat. No. 5,197,879 to Fowler and U.S. Pat. Nos. 5,232,360 and 6,000,941 to Ingels.
The Fowler pliers illustrate the problems involved when utilizing a pinless hinge. The Fowler pliers rely on a dovetail arrangement to hold the pliers parts together over a predetermined extent of opening of the handles and jaws. Beyond that limit, the parts separate from one another, and the pliers fall apart. The relatively short dovetail surfaces also tend to wear due to the squeezing of the handles together.
The Ingels patents provides a hinge that has a pin and a recess which both center the parts and more evenly spread the wear experienced by such parts. The parts are prevented from separating by overhanging shoulders of limited extent, and readily separate when their handles are separated beyond this extent.